DVD editing software -- HELP!

I just transfered some home-made videos to dvd and need to know what kind of video editing software I need to edit clips that will then be placed in PowerPoint. I am planning to use Microsoft's MovieMaker and Producer to combine PowerPoint and video/audio for training purposes. I quickly found that Producer & MovieMaker do not recognize the .vob extension on the dvd files. What do I need to convert to files that Microsoft recognizes? I have downloaded some shareware to get more of an idea of what I need, but it seems that each file I use requires something else (ie; DivX, etc.) I've been searching online for info on this subject and it's mind boggling. I need to purchase this software (yesterday!) and I do not want to make a mistake. Since I am learning as I progress, I would really appreciate being able to ask questions of those of you in the know.